The present invention relates to coating and bonding compositions for threaded connections, such as, for example, for oilfield tool joints, drill collars, casing, tubing, line pipe, flow lines and subsurface production tools. Such a composition may be used with an environmentally friendly lubricating composition providing an environmentally friendly lubricating system, for example, for oilfield uses.
Oilfield thread forms require products with high film strength and a certain range in coefficient of friction. Because thread faces are often subjected to bearing stresses in excess of 50,000 psi, excessive rotation could result in bearing stresses capable of rupturing the protective film and leading to subsequent galling and damage to the pipe. Anti-seize compounds are used to protect against the damage that high bearing stresses may otherwise cause by providing a dissimilar metal or other material between like substrates. Such a compound inhibits the "welding" that may otherwise occur under the pressures and heat incurred during proper make-up.
Conventionally used anti-seize thread compounds include greases which contain substantial amounts of heavy metals or their oxides, carbonates or phosphates. Such metals include: copper, zinc, lead, nickel, molybdenum and aluminum. Recent environmental regulations have begun to discourage, and in some cases prohibit, the use of anti-seize compounds that contain such materials. Organic fluid additives containing antimony, zinc, molybdenum, barium and phosphorus have become the subject of environmental scrutiny as well.
Although it is becoming increasingly unacceptable to include such materials in anti-seize compounds, compounds that do not include them generally do not, by themselves, provide the film strength needed to protect threaded connections from galling or other damage, when subjected to high bearing stresses.
One of the reasons why such compounds are disfavored results from the way they are used. Oilfield threaded connections are usually coated with an excess amount of the thread compound to ensure complete connection coverage. The excess compound is sloughed off so that it ends up downhole. It is then included with the other materials pumped out of the wellhole and into a containment area. From there, material contaminated with heavy metals must be removed to a hazardous waste disposal site.
There is a need for an environmentally friendly lubricating system that still provides adequate protection against galling and other damage to threaded connections subject to high bearing stresses, such as those on oilfield tool joints and drill collars.
There is a need for such a system that provides adequate film strength properties to protect such threaded connections from galling or failure.
There is a need for such a system that reduces the additional downhole make-up of threaded connections used in oilfield drilling operations, such as tool joints and drill collars, which may cause galling or other connection damage.
There is a need for a system for protecting threaded connections, enabling acceptable thread make-up, and restricting downhole make-up that also minimizes the amount of heavy metals leached into the drilling effluent.
There is a need for a system for protecting threaded connections used in drilling operations that should not require hazardous waste classification.
The coating and bonding composition of the present invention enables such a system.